This invention relates to an electronic current sensor and controller for sensing the energization of a load or first electrical utilization device and controlling the operation of a second utilization device remotely located from the first device. More particularly, the invention relates to a current sensor or monitor device for controlling the application of a relatively high level of current to an electrical utilization device from the remote sensing of a relatively low level of current supplied to another electrical utilization device. The invention has various applications in automotive vehicles, such as for an automatic power antenna device which control the extension and retraction of an electric motor driven antenna with the energization and de-energization of the automobile radio receiver.
The controller, which does not require any internal connection to nor any modification of the radio receiver utilization device, provides reliable operation of a control relay from an activating signal voltage as low as ten millivolts developed across a current sensor resistor connected between the vehicle ignition switch and the B+ supply terminal of the receiver, and does not, by reason of its presence, affect or degrade the performance and operation of the receiver. In addition to its aforementioned advantageous characteristics, the controller, which is composed of inexpensive electronic and electrical components, features novel suppression circuits for protection of the electronic components thereof from the otherwise damaging effects of high voltage transients presented to the controller upon the de-energization of various electrical loads in the vehicle and from the inductive components of the controller itself.
The above and other objects, features and advantages of the invention, together with the structural composition and functional operation thereof, will appear from consideration of the following detailed description of the preferred embodiment of the invention made with reference to the accompanying schematic electrical circuit shown in the single figure of the drawings in which the controller 10 is shown as a five terminal, case-grounded structure.